What must a number be able to do?
From the QNG single score to tolerance and blurring: what becomes visible when we open the number up?
Germany · remaining CO₂ budget
Build. Cut carbon. Now.
Remaining CO₂ budget for Germany
–
kg CO₂ remaining
HOW THE NUMBER IS DERIVED →
Why this number?
With every second, the room to act gets smaller.
The remaining CO₂ budget is finite. As long as we keep emitting, it gets smaller – second by second.
That is why this number comes first. It makes visible what is easy to overlook in everyday life: Even while we weigh options, plan and postpone, the starting point is changing.
This does not mean everything has to be forced into change tomorrow. But for me it does mean that business as usual can no longer be the default. Everything that causes avoidable emissions belongs under scrutiny. And whatever can already be done better today does not have to wait until tomorrow.
The countdown is not a forecast. It allocates a scientifically determined global remaining CO₂ budget to Germany and continuously deducts Germany’s current CO₂ emissions. The assumptions are shown openly because a drastic number is only useful if it is clear how it was derived.
Climate target1,5 °C · 50 %
ScopeGermany
Allocationequal share per person
Budget reference date01.01.2026
Emissions rate573.5 Mt CO₂/year · UBA 2025
How the clock is made: Forster et al. (2026) provide global remaining budgets from the beginning of 2026. Germany is assigned 1.1% of that budget, following the equal-per-capita principle used by the German Advisory Council on the Environment (SRU). Since 1 January 2026, the display deducts Germany’s latest official annual CO₂ emissions at a constant rate: 573.5 million t CO₂ for 2025 (UBA). The CO₂ display is therefore not an official real-time measurement, but a transparent projection. The time display divides the remaining German budget by the same constant emissions rate and shows how long that budget would mathematically last if emissions stayed at that level. It is not a forecast. Years and months use average calendar lengths for the running display. The rate is updated when new official emissions data become available.
And what does this mean for building?
What follows for building?
We need something that helps now.
We need to be able to see which emissions a decision triggers today – and which ones we can avoid today. That means assessment tools that make the present visible, instead of letting it disappear inside a single number spread over the next fifty years.
And we need to act. Perhaps that first means: do not build new. Keep building with what exists. Convert. Renovate. Build less. And when we do build new, we need to cause as few new emissions as possible.
What remains once we have avoided what can be avoided?
Then buildings may be able to become something else as well: carbon stores. Using materials that have already removed CO₂ from the atmosphere and keep that carbon in the building. Not only until the first dismantling: components and materials can be reused and carried forward through material cascades. And at the end of that cascade, part of the carbon could, for example, be stored permanently as biochar.
Avoid what we can avoid today. Store what we can store today. And keep the carbon out of the atmosphere for as long as possible.
That is the shortcut.
On bauwen.de I want to find out, step by step, what actually holds up: Where are the decisive points? What helps us decide? And what can we actually do?
Why bauwen.de?
I am an architect. I build.
And I am getting impatient.
The climate crisis will not wait until we have finished discussing everything. So one simple question increasingly occupies me:
What if, from now on, we took “climate action immediately and as much as possible” seriously?
Not as a distant goal, but as the starting point for what we decide, design and build today.
I want to know what that actually means for building. Which of our familiar solutions still hold up? Where do rules and assessment methods create the right incentives – and where perhaps not? Which levers are genuinely large, and which are merely well intentioned? And what could we already be doing differently?
bauwen.de is where I pursue these questions and make public what I find. Drawing on experience from building practice, staying curious about what we may be overlooking – and documenting it as well as I can.
Trying to make the world a little better: with common sense and a decent dose of expertise – that is what I want to try here.